1. Field of the Invention
The present invention relates to a semiconductor device including a high resistance heterojunction diode and a manufacturing method thereof.
2. Description of the Related Art
Conventionally, a technique disclosed in Japanese Patent Application Laid-open No. 2003-318413 has been known as a similar technique of the present invention. In Japanese Patent Application Laid-open No. 2003-318413, an N-type polycrystalline silicon region is formed in a contacting manner on one main surface of a semiconductor base substrate formed with an N−-type epitaxial region on an N+-type substrate region, and the epitaxial region and the N-type polycrystalline silicon region form a heterojunction. On the rear surface of the N+-type substrate region, a rear surface electrode is formed.
In the conventional technique thus configured, when the rear surface electrode is a cathode and the polycrystalline silicon region is an anode, and a current is passed between the cathode and the anode, rectification occurs on a junction interface between the polycrystalline silicon region and the epitaxial region, whereby a diode characteristic is obtained. For example, when the cathode is grounded and a positive electric potential is applied to the anode, a conductive characteristic that corresponds to a forward characteristic of a diode is obtained. On the other hand, when a negative electric potential is applied to the anode, a rejection characteristic that corresponds to a reverse characteristic of the diode is obtained. Both the forward characteristic and the reverse characteristic exhibit a characteristic similar to that exhibited by a Schottky junction configured by a metallic electrode and a semiconductor material.
In such a conventional technique, when an impurity density or a conductivity type of the polycrystalline silicon region is changed, it becomes possible to arbitrarily configure a diode having a predetermined reverse characteristic (forward characteristic corresponding thereto), for example. Thereby, it is more advantageous than a diode configured by the Schottky junction in that a diode of an appropriate breakdown voltage system can be optionally configured.